(a) Field of the Invention
The present invention relates to a process for preparing a heat-resistant thermoplastic resin, more particularly to a process for preparing a heat-resistant thermoplastic resin having superior heat-stability prepared by mixing a graft ABS polymer and a heat-resistant copolymer.
(b) Description of the Related Art
Recently, in order to produce automobile having a lightweight and electric goods requiring heat resistance such as an electric rice cooker, a microwave oven etc., researches on providing heat resistant in acrylonitrile-butadiene-styrene (ABS) resin having superior impact resistance, chemical resistance, and processability etc. have been conducted.
As a method for preparing the ABS resin having a heat resistance discloses preparation by mixing blending a copolymer having a superior heat resistance with a graft ABS polymer has been suggested. As such a method, substituting a part or total amount of styrene used in the preparation of a copolymer having heat-resistance to be kneaded with xcex1-methyl styrene having good heat-resistance (U.S. Pat. Nos. 3,010,936 and 4,659,790), incorporating maleimide compound (Japanese Patent Laid-open publication Nos. sho 58-206657, sho 63-162708, sho 63-235350, and U.S. Pat. No. 4,757,109), blending polycarbonate resin, charging inorganic material etc. are known.
However, the method of using maleimide compound to give heat resistant and the method of blending polycarbonate resin have the problem of reducing processability and are not economical due to expensive cost. The method charging inorganic material has a defect in that the impact strength is suddenly reduced. Therefore, the method for preparing a-methyl styrene copolymer by emulsion polymerization and blending it with graft ABS resin is widely used. Although this method is economical and can obtain superior impact resistance, due to the emulsion polymerization of a-methyl styrene reactivity is low and heat stability is low, and thus a lot of gases are generated and gloss property deteriorates during the processing of the resin.
It is an object of the present invention to provide a method for preparing a thermoplastic resin having excellent heat-resistance, thermal stability, impact resistance, and processability.
In order to achieve the object, the present invention provides a method for preparing a thermoplastic resin composition having excellent heat-resistance and heat stability comprising the steps of:
a) preparing a graft ABS polymer by an emulsion polymerization of:
i) 40 to 70 wt parts of conjugated diene rubber latex;
ii) 15 to 40 wt parts of aromatic vinyl compound; and
iii) 5 to 20 wt parts of vinyl cyanide
b) preparing a copolymer having heat-resistance by a mass polymerization of:
i) 50 to 80 wt parts of aromatic vinyl compound; and
ii) 20 to 50 wt parts of vinyl cyanide; and
c) blending the graft ABS polymer and the copolymer having heat-resistance.